chr15-48445469-A-G

Variant names:

• chr15-48445469-A-G
• rs1555395762
• NM_000138.5:c.5824T>C

Variant summary

Our verdict is Pathogenic. Variant got 19 ACMG points: 19P and 0B. PM1 PM2 PM5 PP2 PP3_Strong PP5_Very_Strong

The NM_000138.5(FBN1):​c.5824T>C​(p.Cys1942Arg) variant causes a missense change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. C1942F) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 31)
• Consequence: FBN1 NM_000138.5 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 7.12

Genes affected

FBN1 (HGNC:3603): (fibrillin 1) This gene encodes a member of the fibrillin family of proteins. The encoded preproprotein is proteolytically processed to generate two proteins including the extracellular matrix component fibrillin-1 and the protein hormone asprosin. Fibrillin-1 is an extracellular matrix glycoprotein that serves as a structural component of calcium-binding microfibrils. These microfibrils provide force-bearing structural support in elastic and nonelastic connective tissue throughout the body. Asprosin, secreted by white adipose tissue, has been shown to regulate glucose homeostasis. Mutations in this gene are associated with Marfan syndrome and the related MASS phenotype, as well as ectopia lentis syndrome, Weill-Marchesani syndrome, Shprintzen-Goldberg syndrome and neonatal progeroid syndrome. [provided by RefSeq, Apr 2016]

ACMG classification

Verdict is Pathogenic. Variant got 19 ACMG points.

• PM1: In a disulfide_bond (size 14) in uniprot entity FBN1_HUMAN there are 5 pathogenic changes around while only 0 benign (100%) in NM_000138.5
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr15-48445468-C-A is described in Lovd as [Likely_pathogenic].
• PP2: Missense variant in the FBN1 gene, where missense mutations are typically associated with disease (based on misZ statistic). The gene has 1311 curated pathogenic missense variants (we use a threshold of 10). The gene has 112 curated benign missense variants. Gene score misZ: 5.0644 (above the threshold of 3.09). Trascript score misZ: 8.1787 (above the threshold of 3.09). GenCC associations: The gene is linked to MASS syndrome, Weill-Marchesani syndrome, geleophysic dysplasia, Shprintzen-Goldberg syndrome, Acromicric dysplasia, familial thoracic aortic aneurysm and aortic dissection, progeroid and marfanoid aspect-lipodystrophy syndrome, ectopia lentis 1, isolated, autosomal dominant, Marfan syndrome, Weill-Marchesani syndrome 2, dominant, isolated ectopia lentis, neonatal Marfan syndrome, stiff skin syndrome.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.993
• PP5: Variant 15-48445469-A-G is Pathogenic according to our data. Variant chr15-48445469-A-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 811411.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
FBN1	NM_000138.5	c.5824T>C	p.Cys1942Arg	missense_variant	Exon 48 of 66	ENST00000316623.10	NP_000129.3
FBN1	NM_001406716.1	c.5824T>C	p.Cys1942Arg	missense_variant	Exon 47 of 65		NP_001393645.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
FBN1	ENST00000316623.10	c.5824T>C	p.Cys1942Arg	missense_variant	Exon 48 of 66	1	NM_000138.5	ENSP00000325527.5

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 31

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not specified Pathogenic:1

Apr 25, 2019

ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The FBN1 c.5824T>C; p.Cys1942Arg variant, to our knowledge, is not described in the medical literature or in gene-specific databases. It is also absent from general population databases (Exome Variant Server and Genome Aggregation Database), indicating it is not a common polymorphism. This variant occurs in a cysteine residue in one of the calcium binding EGF-like domains of fibrillin-1 (Wu 1995). Each EGF-like domain contains six highly-conserved cysteines and the disulfide bridges formed between these residues are essential for protein folding; loss of one of these cysteines may interfere with proper disulfide bridge formation, disrupting protein structure. Accordingly, the revised Ghent nosology for Marfan syndrome lists missense variants of cysteine residues as one of the criteria for classification of a variant as pathogenic (Loeys 2010). Based on available information, this variant is considered likely pathogenic. REFERENCES Loeys et al. The revised Ghent nosology for the Marfan syndrome. J. Med. Genet. 2010 47(7): 476-85. Wu et al. Fibrillin domain folding and calcium binding: significance to Marfan syndrome. Chem. Biol. 1995 2(2):91-7. -

Marfan Syndrome/Loeys-Dietz Syndrome/Familial Thoracic Aortic Aneurysms and Dissections Pathogenic:1

Apr 25, 2022

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: FBN1 c.5824T>C (p.Cys1942Arg) results in a non-conservative amino acid change located in the EGF-like domain (IPR000742) of the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. In addition, this variant occurs in a cysteine residue in EGF-like domain and the sulfhydryl group of cysteine is unique in its ability to participate in disulfide covalent cross-linkage. In fact, two-thirds of fibrillin cysteine residues exist in the half-cystinyl form, suggesting their participation in intramolecular disulfide linkage (Dietz_1992). Therefore, the substitution of a cysteine may disrupt the structure of the FBN1 protein, affecting its function. The variant was absent in 250846 control chromosomes (gnomAD). c.5824T>C has been reported in the literature in at least one individual affected with Marfan Syndrome (Xu_2019). The data indicate that the variant may be associated with disease. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. One ClinVar submitter (evaluation after 2014) cites the variant as likely pathogenic. Based on the evidence outlined above, the variant was classified as likely pathogenic. -

Marfan syndrome;C4707243:Familial thoracic aortic aneurysm and aortic dissection Pathogenic:1

Mar 10, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

For these reasons, this variant has been classified as Pathogenic. This sequence change replaces cysteine, which is neutral and slightly polar, with arginine, which is basic and polar, at codon 1942 of the FBN1 protein (p.Cys1942Arg). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with Marfan syndrome (PMID: 31830381). ClinVar contains an entry for this variant (Variation ID: 811411). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt FBN1 protein function. This variant affects a cysteine residue in the EGF-like, TGFBP or hybrid motif domains of FBN1. Cysteine residues are believed to be involved in intramolecular disulfide bridges and have been shown to be important for FBN1 protein structure (PMID: 16905551, 19349279). In addition, missense substitutions affecting cysteine residues within these domains are significantly overrepresented among patients with Marfan syndrome (PMID: 16571647, 17701892). This variant disrupts the p.Cys1942 amino acid residue in FBN1. Other variant(s) that disrupt this residue have been observed in individuals with FBN1-related conditions (PMID: 31830381; Invitae), which suggests that this may be a clinically significant amino acid residue. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.57	D
BayesDel_noAF	Pathogenic	0.58
CADD	Pathogenic	27
DANN	Uncertain	1.0
Eigen	Pathogenic	1.0
Eigen_PC	Pathogenic	0.91
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.92	D
M_CAP	Pathogenic	0.89	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Pathogenic	0.96	D
PrimateAI	Pathogenic	0.86	D
PROVEAN	Pathogenic	-11	D
REVEL	Pathogenic	0.97
Sift	Pathogenic	0.0	D
Sift4G	Uncertain	0.0060	D
Vest4		0.85
MutPred		0.93		Gain of disorder (P = 0.0308);
MVP		0.98
MPC		1.8
ClinPred		1.0	D
GERP RS		5.8

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.0		Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs1555395762; hg19: chr15-48737666;